Differences between current version and revision by previous author of random(4).
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| Newer page: | version 2 | Last edited on Monday, August 23, 2004 8:19:38 pm | by StuartYeates | |
| Older page: | version 1 | Last edited on Monday, June 3, 2002 6:55:43 pm | by perry | Revert |
@@ -14,9 +14,9 @@
!!DESCRIPTION
The character special files __/dev/random__ and
-__/dev/urandom__ (present since Linux 1.3.30) provide an
+__/dev/urandom__ (present since [
Linux]
1.3.30) provide an
interface to the kernel's random number generator. File
__/dev/random__ has major device number 1 and minor
device number 8. File __/dev/urandom__ has major device
number 1 and minor device number 9.
@@ -55,33 +55,43 @@
with the following commands:
mknod -m 644 /dev/random c 1 8
-mknod -m 644 /dev/urandom c 1 9
-chown root:root /dev/random /dev/urandom
+
mknod -m 644 /dev/urandom c 1 9
+ chown root:root /dev/random /dev/urandom
+
When a Linux system starts up without much operator interaction, the entropy pool may be in a fairly predictable state. This reduces the actual amount of noise in the entropy pool below the estimate. In order to counteract this effect, it helps to carry entropy pool information across shut-downs and start-ups. To do this, add the following lines to an appropriate script which is run during the Linux system start-up sequence:
+ echo "Initializing kernel random number generator..."
+ # Initialize kernel random number generator with random seed
+ # from last shut-down (or start-up) to this start-up. Load and
+ # then save 512 bytes, which is the size of the entropy pool.
+ if [[ -f /var/random-seed ]; then
+ cat /var/random-seed >/dev/urandom
+ fi
+ dd if=/dev/urandom of=/var/random-seed count=1
+
+Also, add the following lines in an appropriate script which is run during the Linux system shutdown:
- echo
-Also
, add the following lines in an appropriate script
which is run during
the Linux system shutdown:
+ # Carry a random seed from shut-down to start-up for the random
+ # number generator. Save 512 bytes
, which is the size of the
+ # random number generator's entropy pool.
+ echo "Saving random seed..."
+ dd if=/dev/urandom of=/var/random-seed count=1
- # Carry a random seed from shut-down to start-up for the random
-# number generator. Save 512 bytes, which is the size of the
-# random number generator's entropy pool.
-echo
!!FILES
/dev/random
/dev/urandom
!!AUTHOR
-The kernel's random number generator
was written by Theodore
+The kernel's RandomNumberGenerator
was written by Theodore
Ts'o (tytso@athena.mit.edu).
!!SEE ALSO
-mknod (1)
+mknod(1)
RFC 1750,
----
